This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from my application LASER SCANNING APPARATUS filed with the Korean Industrial Property Office on Jul. 31, 1999 and there duly assigned Serial No. 31548/1999.
The present invention relates, in general, to laser scanning apparatuses and, more particularly, to a laser scanning apparatus that has a rotating guide instead of a polygon mirror so as to scan laser beams in a scanning direction at a constant velocity.
In general, a laser scanning apparatus is employed in a laser printer, a facsimile, etc. The laser scanning apparatus is an optical device that traverses a surface with laser beams so as to reproduce or transmit a desired image in the form of dots, or traverses a document or the like with laser beams so as to read data on the document or the like for use by a computer or computerized device.
A laser scanning apparatus can include a laser beam source, various lenses, and a polygon mirror for deflecting the laser beam and directing it through various optical devices toward a receiving element, such as a photosensitive drum. Such an apparatus has several disadvantages.
For example, such a laser scanning apparatus operates in such a manner as to require extreme precision in the fabrication of its component parts (for example, the polygon mirror and the various lenses or other optical elements). Moreover, a great degree of precision is required in the manufacture of reflecting surfaces used in such an apparatus. Finally, extreme precision in the assembly of the apparatus is required, and the assembly can be complex and difficult. All of these requirements tend to increase the cost of manufacture of such a product.
Accordingly, the present invention has been developed with the above problems in mind, and an object of the present invention is to provide a laser scanning apparatus which is relatively simple to manufacture and assemble, and which has reduced manufacturing cost. This is achieved principally by elimination of the polygon mirror.
In order to accomplish the above object, the present invention provides a laser scanning apparatus, comprising: a light source for emitting laser beams; a deflecting unit for deflecting laser beams emitted from the light source to a scanning direction; a rotating guide having a plurality of guide holes for scanning laser beams at a constant velocity, the rotating guide accommodating the deflecting unit and being positioned so that the light source lies on a central axis of the rotating guide; a drive motor for rotating the rotating guide while it is engaged with the rotating guide; and an image forming arrangement for focusing the laser beams which having passed through the guide holes of the rotating guide onto a surface.
Preferably, the deflecting unit includes a conical mirror which is mounted on the central axis of the rotating guide, and which has a surface inclined at a certain angle.
Preferably, the deflecting unit further includes a collimating lens for collimating the laser beams emitted from the light source so that they are parallel with one another as they proceed toward the conical mirror, the collimating lens being mounted between the light source and the conical mirror.
Preferably, the deflecting unit further includes a direction restricting unit for restricting the progressive direction of laser beams deflected by the conical mirror within a scanning direction.
Preferably, the direction restricting unit is cylindrically shaped, is closed at its bottom and open at its top, and has an opening for restricting the direction of transmission of the laser beams deflected by the conical mirror to a scanning direction.
Preferably, light absorbing material is applied to the inner surface of the sidewall of the direction restricting unit, the conical mirror is fixed to the bottom of the direction restricting unit, and the width of the opening of the restricting unit coincides with the effective scanning width in a scanning direction.